The present invention relates to an apparatus for optically and continuously detecting the distance between a preceding car and one's own car by image sensors.
Japanese Examined Patent Publication Nos. Sho-63-38085 (1988) and Sho-63-46363 (1988) disclose image sensors for optically detecting the distance between cars going in the same direction.
In these Japanese Publications, it is proposed to employ a pair of left- and right-hand optical systems as shown in FIG. 6, these left- and right-hand optical systems having respective lenses 1 and 2 that are separated by a base length of L.
Discrete image sensors 3 and 4 are provided at the respective positions of focal length f of the lenses 1 and 2, respectively, and a signal processor 30 is provided for sequentially shifting the picture signals supplied from the image sensors 3 and 4 for electrical superposition. A distance R up to an object 31 is obtained from a shift quantity l taken when the two picture signals are synchronized by triangulation, wherein: ##EQU1##
Japanese Examined Patent Publication No. Sho-60-33352 (1985) discloses a technique of tracking the preceding car image picked up by image sensors or the like.
Wherein a target is tracked by an operator who sets a tracking gate (window) encompassing the target on a display screen while watching the display screen.
The conventional apparatus for detecting the distance between cars, as described above, measure only the distance to the object in the direction of an optical axis of the apparatus.
Thus, to measure the distance to a moving object with the conventional apparatus mounted on one's own car, for instance, the optical axis of the apparatus must be adjusted to direction of the moving object.
As the distance to the object is measured by comparing the images picked up by the pair of left-hand and right-hand optical systems, a problem results in that, when it is attempted to measure the distance to the preceding car, if another car is going on the left or right of the preceding car in parallel, thereto the driver will be unable to perceive which one of the cars is being used for the measurement of the distance thereto.